Film-forming silane crosslinked acrylate interpolymers having water-barrier properties

ABSTRACT

Polymeric compositions having desirable film-forming characteristics and water-barrier properties at substantially neutral pH&#39;s and yet solubilizable and thus disposable at substantially non-neutral pH&#39;s comprise a silane crosslinked interpolymer of an alkyl acrylate and a monomer interpolymerizable therewith such as, in the preferred alkaline labile embodiment, acrylic acid. The silane crosslinking monomer is preferably 3-(trimethoxysilyl)-propyl methacrylate or 3-(trimethoxysilyl)-propyl acrylate. The resultant pH-sensitive polymeric composition may be used, for example, as a binder for other materials, such as webs of non-woven water-dispersible fibers, or may be used in film form either by itself or preferably laminated to other dispersible materials to produce a variety of products which are completely disposable at selected non-neutral pH&#39;s.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of my copending applicationSer. No. 90,539, Filed Nov. 18, 1970, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to polymers and methods of producing thesame, the polymers having film-forming characteristics and the filmsproduced therefrom having water-barrier properties at substantiallyneutral pH's and yet being substantially completely solubilizable atnon-neutral pH's. More particularly, the invention relates tosilane-crosslinked interpolymers of alkyl acrylates and, in a preferredembodiment, acrylic acid, and disposable products produced therefrom.

While the composition and products of the present invention are hereindescribed primarily in connection with advantageous applications in themedical and sanitary product fields, it should be understood that thepresent invention is not limited thereto. In the light of the presentdisclosure, those skilled in the art will recognize a variety ofapplications in other fields wherein the moisture impermeability andfilm-forming characteristics of the alkaline-labile or acid-labilesilane-crosslinked polymers of the present invention may beadvantageously employed.

2. Description of the Prior Art

There has long been a need in the handling of waste products of theliquid or semi-liquid type, such as body exudates, to have a materialwhich would contain the waste when excreted but which could then bereadily disposed of later. In hospital use, for example, there arebedpans, urinals, emesis basins, bags for wound irrigation, bags forincision and drainage of abscesses, bags for urine collection, bags forostomies, i.e., ileostomies, colostomies, etc., and other containerswhich are used daily for the collection of body exudates in a liquid orsemi-liquid form. Similarly, in home use, body exudates are collected inbandages, pads, diapers and similar sanitary products. The problem ofconvenient, sanitary, esthetic and inexpensive disposal is ever present.

One prior art approach has been to utilize various plastic materials,such as polyethylene, to form water-impervious containers, barriers orliners for collection of the body exudates. The waste material and theplastic film can then be dropped into a toilet bowl and the liquid orsemi-liquid waste flushed away. But the problem of disposal of theplastic film, which is not soluble, still exists. The film can not beflushed away without ultimately causing plumbing and sewage treatingproblems. Instead, it is retained and collected in containers, thecontents of which are later incinerated or dumped into a trash disposalarea. Quite aside from the esthetic problem and the attendantinconvenience and cost, the practice is undesirable from the standpointof possible spread of contamination or disease.

Another prior art approach is described in U.S. Pat. No. 3,480,016,issued Nov. 25, 1969, and entitled "Sanitary Products". This patentdiscloses, for example, toilet-flushable sanitary products comprisingbiodegradable fibers bonded together by a resin. The resin is stable tobody discharges which have pH's ranging from about 4.6 to about 8.4, butis solubilizable under selected acid or alkaline conditionssubstantially outside this range. The polymers employed, however, areunduly hydrophilic in nature and in practice do not form films havingtrue moisture-barrier properties. Accordingly, while the polymers, aswell as associated absorbent materials, can be disposed of along withthe waste material by solubilizing the same, certain applicationsrequire the presence of a supplementary moisture barrier, thus renderingthe product not truly disposable in its entirety and complicating thedisposal problem, as already described. That is, the polymers describedin U.S. Pat. No. 3,480,016 are not crosslinked in any manner and are notsuitable for forming films with water barrier properties, but can onlybe used as binders for "sanitary products".

British Pat. No. 1,127,625 discloses generally the use ofalkoxy-silyl-alkyl monomers as crosslinking agents for polymers such asacrylate polymers for pressure-sensitive adhesives. This patent,however, contains no suggestion either of producing films havingwater-barrier properties at neutral pH's that are also solubilizable inaqueous media at substantially non-neutral pH's, nor of the particularsilane monomers and proportions thereof that I have found to becritical, in accordance with the present invention, for producingpolymers from which such films can be manufactured.

OBJECTS OF THE INVENTION

It is therefore a general object of the present invention to cope withthese and other problems of the prior art. It is another general objectto provide a polymeric composition having desirable film-formingcharacteristics and water-barrier properties at substantially neutralpH's and yet being solubilizable at substantially non-neutral pH's. Itis another general object to avoid the hydrophilic nature of prior-artpH-sensitive films and to provide polymeric films having water-barriercharacteristics at substantially neutral pH's, said films beingotherwise solubilizable at substantially non-neutral pH's.

It is a specific object of the present invention to provide sanitaryproducts, including bags, vessels, liners, pads and the like, whichcontain or otherwise hold body exudates and have water-barrierproperties at neutral pH's so as to prevent seepage or leakage but areotherwise completely dispersible or solubilizable at substantiallynon-neutral pH's. It is another specific object of a preferredembodiment of the invention to provide a polymeric composition havingwater-barrier properties at pH's substantially below about 9 and yetbeing completely solubilizable at pH's substantially above about 9.

It is a still further object to provide composite or laminated sanitaryproducts from pH-sensitive, water-impermeable, heat-sealablethermoplastic polymers in combination with other water dispersiblematerials to form completely disposable sanitary products. These andother objects of the present invention will become apparent as thedetailed description proceeds

SUMMARY OF THE INVENTION

These objects are achieved in a particular embodiment by providing apolymeric composition comprising a silane crosslinked interpolymer ofcertain ethylenically unsaturated monomers herein set forth. The silanecrosslinking agent attenuates the hydrophilic nature of the interpolymerand imparts the desired water barrier properties to the films producedtherefrom at substantially neutral pH's, e.g., pH's in the range ofabout 4.5 to about 8.5. Yet, in substantially alkaline or acidsolutions, the polymeric composition is completely solubilizable andthus conveniently disposable.

DESCRIPTION OF THE PREFERRED EMBODIMENTS THE INTERPOLYMER

The interpolymer is made up of a first monomer selected from the groupconsisting of alkyl acrylates, the alkyl group having one to eightcarbon atoms, e.g., methyl acrylate, ethyl acrylate, etc., preferablyethyl acrylate, and a second monomer which is selected to achieve theparticular alkaline or acid labile characteristic desired. In thepreferred alkaline labile embodiment, wherein the polymeric compositionis solubilizable in aqueous alkaline solutions having pH's substantiallyabove about 9, e.g., 10 or higher, usually 12 or higher, the secondmonomer is an acid comonomer selected from the group consisting ofacrylic acid, methacrylic acid, fumaric acid, maleic acid, maleicanhydride and itaconic acid. The preferred acid comonomer is acrylicacid. In the acid labile embodiment, wherein the polymeric compositionis solubilizable in acidic solutions having pH's substantially belowabout 4.5, i.e., pH's of 4 or lower, the second monomer is selected fromthe group consisting of dimethylaminoethyl acrylate, dimethylaminoethylmethacrylate, diethylaminoethyl acrylate, diethylaminoethylmethacrylate, tert.-butylaminoethyl acrylate and tert.-butylaminoethylmethacrylate, and is preferably dimethylaminoethyl methacrylate. Itwill, of course, be understood that mixtures of each of the foregoinggroups of monomers may be used.

The proportions of the first monomer and second monomer depend in partupon the particular monomers employed and the characteristics desired inthe resulting silane crosslinked interpolymer. In general, the firstmonomer is present in the proportion of about 0.5 to 5 parts by weightper part of second monomer, preferably about 1.5 to 4 parts by weightper part of second monomer. Within these ranges the proportions may bevaried to impart desired characteristics. For example, increasing theproportion of methacrylic acid or acrylic acid, which are hardeningmonomers, increases the rate at which the interpolymer dissolves innon-neutral solutions, but also decreases flexibility, and vice versa.

Similarly, the particular selection of monomers employed cansignificantly affect properties. For example, the longer chain alkylacrylates impart greater flexibility to the resulting film but alsoincrease tackiness and decrease the rate at which the film will dissolvein non-neutral solutions. Likewise, the use of methacrylic acid insteadof acrylic acid produces a stiffer interpolymer.

THE CROSSLINKING MONOMERS

The essential crosslinking monomers contain both an ethylenic linkageand an alkoxysilyl or acyloxysilyl group. These monomers interpolymerizethrough their ethylenic linkages, thereby becoming incorporated in theinterpolymer backbone. The polymers remain linear, soluble anduncrosslinked until crosslinking is made to take place through reactionof the alkoxysilyl or oxysilyl groups pendant from the polymer backbone,as hereinafter set forth.

Various crosslinking monomers of the above mentioned type have beenused, including 3-(trimethoxysilyl)-propyl acrylate,3-(trimethoxysilyl)-propyl methacrylate, allyl trimethoxysilane, vinyltriethoxysilane and vinyl triacetoxysilane, as set forth in the exampleshereinafter. While each of these compounds, upon crosslinking,introduces a crosslinked, solvent-insoluble gel structure into theinterpolymer film, it is found that, of the above-listed crosslinkingmonomers, only the 3-(trimethoxysilyl)-propyl acrylate and3-(trimethoxysilyl)-propyl methacrylate are effective in producing filmswith good water barrier properties.

More particularly, the crosslinking agents suitable for use in theinterpolymer compositions of the present invention, of which the lattertwo crosslinking agents are preferred, include the silane monomershaving the structural formula: ##EQU1## wherein:

R is selected from the group consisting of CH₃ --, CH₃ CH₂ --, CH₃ O--and CH₃ CH₂ O--;

R₁ and R₂ are each selected from the group consisting of CH₃ -- and CH₃CH₂ --;

R₃ is selected from the group consisting of H--, CH₃ -- and CH₃ CH₂ --;and n is 0 or a positive integer not greater than 8.

Since the number of crosslinks obtained in the polymeric composition isproportional to the concentration of silane monomer used therein, atleast about 0.7% by weight, based upon the combined weight of the firstand second monomer, of the crosslinking agent should be employed toachieve the desired water barrier property. Concentrations substantiallyless than 0.7%, e.g., 0.25% and 0.5%, have resulted in unsatisfactorywater barrier properties. The upper concentration limit for the silanecrosslinking agent is in the range of from about 2 to 3%, amountssubstantially in excess thereof causing instability and undesiredgelation during polymerization. The preferred range is from about 0.9 toabout 1.5%.

MODIFYING AGENTS

Compatible modifying agents may also be incorporated into thecompositions of the present invention to achieve desired productcharacteristics, as will be apparent to those skilled in the art. Suchmodifying agents must, of course, not unduly affect the basiccharacteristics of the interpolymer, particularly its solubility atselected pH's. Manifestly, the modifying agents must themselves also besoluble at the selected solubilizing pH's.

As an example, in the acid labile embodiment, N-isopropylacrylamide maybe incorporated to decrease the surface tack of the resulting film. Forsuch purposes, as much as about 5 to 25% by weight, based on the totalweight of the polymer, may be incorporated in the composition.Similarly, to offset the tendency of the alkaline labile or acid labilesilane crosslinked interpolymers to crack if repeatedly flexed underconditions of low humidity, it has been found desirable to incorporatetherein about 1 to 20% by weight, based on the total weight of thepolymer, preferably about 2 to 10%, of a humectant-type plasticizer.Plasticizers suitable for this purpose include glycerine, diethyleneglycol, triethylene glycol, propylene glycol, dipropylene glycol andtripropylene glycol.

Still other plasticizers may be advantageously employed for particularpurposes. For example, when the films of the present invention areformed by casting a solution of the polymer on a substrate, the releaseof the film from the substrate can be substantially facilitated by firstadding to the interpolymer composition a plasticizer having releaseagent properties. Suitable plasticizers having release agent properties,which also dissolve readily in aqueous alkaline solutions, are the longchain monocarboxlic fatty acids, such as lauric, myristic, and palmiticacids. For such purposes, at least about 1% by weight, based on thetotal weight of the polymer, of the plasticizer should be employed,preferably about 2 to 10%. Since such plasticizers have no apparentundesirable effects on the water-barrier properties of the film, as muchas 20% plasticizer may also be used, although such higher amountsprovide no particular improvement in film properties or releasecharacteristics.

In a preferred embodiment, both a humectant-type plasticizer and aplasticizer having release agent properties are employed. Thus, films ofthe present invention having excellent properties with respect to bothflexibility and improved release are obtained by incorporating about 2to 10% by weight of each type of plasticizer in the polymericcomposition, e.g., 5% of glycerine and 5% of lauric acid.

METHOD OF PREPARATION

The silane crosslinked polymers of the present invention may beprepared, for example, by solution polymerization of the first andsecond monomers, e.g., acrylic acid and ethyl acrylate, in the presenceof the silane crosslinking agent, e.g., 3-(trimethoxysilyl)-propylmethacrylate. The solvent is preferably an organic solvent having aboiling point not substantially in excess of about 100°-110°C, such as,for example, ethyl acetate, toluene, benzene, methyl ethyl ketone, orthe like.

In a preferred embodiment, the solvent may also include isopropanol,which has the unique property of acting both as a solvent and astabilizing agent whereby undesired gelation of the solution isprevented. Typical proportions of solvent and points of addition will beevident from the specific examples herein.

After the first and second monomers and crosslinking agent are admixedin the solvent, the solution is stirred and swept with nitrogen, and itstemperature is raised to about 75°C. A catalytic amount of apolymerization catalyst, e.g., a vinyl polymerization initiator such as2,2'-azobis-(2-methylpropionitrile) or the like, is added and thenitrogen flow discontinued. The exothermic polymerization reactionproceeds with vigorous refluxing, the temperature rising to about80°-90°C. After the exothermic polymerization has subsided, stirring andheating to maintain the temperature at about 80°C continues for severalhours to assure substantially complete polymerization.

During the polymerization reaction, the alkoxy silane crosslinkingmonomer interpolymerizes with the other monomers. The crosslinkingreaction does not, however, occur until the polymer solution is dried bydriving off the solvent. In a preferred embodiment, wherein the productis produced in film form, the polymer solution is first diluted to asolids content of less than about 35% by weight, e.g., about 30%, andplasticizers are added. It is then spread in one or more thin coats on arelease surface such as silicone-coated paper or polyethylene-coatedpaper with air drying between coats, drying preferably being completedat elevated temperatures, e.g., about 50° to 100°C.

The crosslinking reaction is accelerated by drying at elevatedtemperatures. It may also be accelerated by the presence of catalyticamounts (e.g., about 0.5% by weight, based on the weight of theinterpolymer) of a catalyst known to promote certain siloxanecondensation reactions. Examples of suitable accelerant catalysts arezinc, stannous, lead and iron octoates, and dialkyl tin carboxylatessuch as dibutyl tin dilaurate and dibutyl tin di-2-ethylhexoate.

The thickness of the film may be adjusted by varying the solids contentof the solution, by varying the thickness of each layer of the depositedsolution, by varying the number of layers or by a combination of thesetechniques, or the like. Film thicknesses are typically in the range ofabout 1 to 20 mils, preferably 2 to 10 mils. Because flexibility is inpart a function of film thickness, the thinner-walled films are employedwhere a high degree of flexibility is desired. The thinner-walled filmsalso reduce material costs.

In a dry state, the resulting films are clear, flexible and havesurfaces which may be slightly cohesive. Under humid conditions, thesurfaces may become more cohesive due to moisture absorption. Becausethe film may thus block to itself on long standing, particularly undermoist conditions, it should preferably be stored with an interliner suchas silicone coated paper, polyethylene or polyethylene-coated paper. Aswill be apparent hereinafter, the blocking problem may otherwise becoped with when the film is laminated with other nonblocking materialsto form composite products.

Further specifics as to the preparation of the product of the presentinvention will be apparent from the examples, many details otherwisebeing within the skill of the art in the light of this disclosure.

DISPOSAL SOLUTIONS

As previously indicated, the polymers of the present invention and filmsformed therefrom are solubilizable in aqueous alkaline or acidsolutions, preferably solutions having pH's of about 12 or higher orabout 3 or lower, respectively, depending on the particular embodiment.In the preferred alkaline labile embodiment, solutions of strongalkalis, such as lithium, sodium and potassium hydroxides, disintegrateand dissolve the film most rapidly, sodium hydroxide being the preferredalkali.

Sodium carbonate solutions or ammonia solutions will dissolve the film,but the rate of solution is much slower, e.g., less than half the rate.Moreover, the concentration of ammonia or sodium carbonate solutionsrequired to dissolve the film, e.g., about 1 to 10% by weight, is higherthan the concentration of sodium hydroxide solutions, e.g., about 0.5%,as will be apparent from Example 1 hereinafter.

It should be noted that solutions of divalent alkaline earth hydroxides,such as calcium or barium, are unsuitable. They interact with thecarboxyl groups on adjacent chains in the polymer, further crosslinkingthe polymer and thus interfering with the solubilizing of the same.

In the acid labile embodiment, hydrochloric acid of 4 to 6 normalconcentration (12 to 18% HCl) is the preferred solubilizing solution toobtain as rapid a break-up of the film into pieces as possible. The 4 to6 normal concentration softens and swells the film faster than lower orhigher concentrations of this acid. Even 1 normal hydrochloric acid (3%HCl) will ultimately dissolve the film completely, but its action indisintegrating the film to flushable pieces is much slower than that of4 normal acid.

Sulfuric acid solutions at any concentration from 1 to 20 normal aremuch poorer than hydrochloric acid solutions for disintegrating thefilm. Any concentration of sulfuric acid from 2 normal up will, however,ultimately dissolve the film. Solutions of sodium acid sulfate orpotassium acid sulfate do not soften or dissolve the film and are to beavoided.

In practice, the alkaline labile or acid labile interpolymers andproducts produced therefrom are readily disposed of by depositing thesame with the waste products contained therein in a toilet bowl, addingthe requisite sodium hydroxide or hydrochloric acid to achieve pHadjustment, and shortly thereafter flushing the entire contents. Nomessy handling is otherwise involved.

COMPOSITE PRODUCTS

The thermoplastic nature of the polymeric compositions of the presentinvention, whether in the form of films or otherwise, lends itself tothe formation of composite products, the components of which complementone another. This is illustrated, for example, by laminating films ofthe present invention to fiber webs having substantially no wetstrength, the resulting composite solving several problems associatedwith the free standing films, as described in the following paragraphs.

The rate of solution of the silane-crosslinked polymer films isdependent to some degree on the thickness of the film being used. As aresult, it is highly desirable to use as thin a film as practical inmaking disposable products. One problem with extremely thin films,however, is that as the films become thinner the strength of the film isproportionately decreased. Even though films having excellent waterbarrier properties can be formed with a thickness as low as 2 mils, theyare relatively weak. This problem is aggravated by adsorbed or imbibedwater which acts as a plasticizer, making the film more readilyextensible and thereby weaker.

A further problem is that, as aforementioned, the films are somewhatcohesive and are difficult to handle when rolled or otherwise placedtogether. It thus becomes necessary to use release interliners toprevent sticking.

These problems are solved by the aforementioned composite formed bylaminating the film to a fiber web such as cellulosic paper. In thepreferred practice, papers are used which have relatively high drystrength, for example, 100 to 200 grams/inch-width in the cross machinedirection and 300 to 500 grams/inch-width in the machine direction. Thepreferred fiber webs have little or no wet strength and readilydisintegrate and become flushable in a toilet system, as is presentlydone with commercially available toilet papers. Papers with greater drystrength than above indicated are preferred provided the wet strength issufficiently low to permit flushing. Because the stiffness of the paperis incorporated into the final laminate product, relatively thin,flexible papers are preferred in those embodiments wherein flexibilityis a desirable attribute.

If desired, the fibrous sheet can be formed of a web of relatively-longfibers which are randomly laid to give strength in all directions.Fibers of this type are, for example, those utilized in making non-wovenfabrics, where fiber lengths of 1/2 inch or greater are generally used.Alternatively, the fibers may be highly "oriented" or "parallelized" toachieve desired characteristics.

In preparing the fiber-film laminate, the film is first cast from asolvent onto a release paper and then dried and cured, as previouslydescribed. While still on the carrier paper, the film is pressed intointimate contact with the fiber web while being subjected to sufficientheat and pressure to soften the film and bond the film to the web attheir contacting surfaces In forming the laminate, however, care shouldbe used so that the film is not completely penetrated by fibers of thefiber web as this would destroy the integrity of the film and thus causeleakage in the final film-fiber laminate.

The bonded fiber web substantially increases the dry strength of thefilm, and also eliminates the problem of tackiness and the need for aninterliner. In utilizing the film-fiber laminate for containing bodyexudates or other aqueous liquids, the fiber portion of the laminate isdisposed exteriorly. The film thus acts as a moisture barrier and thefiber portion remains dry and retains its dry strength until depositedin a toilet bowl or the like.

If it is desired to make water-impermeable sheets which present noproblem with respect to tack or tackiness, a fiber web may be laminatedto both sides of the film. This may be conveniently done by passing thepaper-film-paper composite between a laminating nip of heated metalrolls. The fiber web on the side of the laminate which is to be incontact with liquids is preferably light weight and of minimumstiffness. Since the web is being used only as a protective blockinglayer and is wetted by the contained liquids, its dry strength isimmaterial.

Another advantageous composite product application for the polymericcomposition of the present invention is as a binder in the formation ofwater-permeable, non-woven fabric or mats. The non-woven fabric is heldtogether in the presence of substantially neutral solutions by thepolymeric composition of the present invention. The polymer may bedistributed throughout the fibers. Alternatively, the polymer may bedistributed in a plurality or multiplicity of discrete deposits invarious shapes and binder patterns and in sufficient amounts to bind thenon-woven fabric together.

Impregnation of the non-woven fabric with the polymer may be byconventional techniques well within the skill of the art in the light ofthis disclosure. Patterns for binding the fabric together may includethose taught in the prior art, such as in the non-woven fabrics of U.S.Pat. Nos. 2,705,687, 2,782,130 and 3,009,823.

Still another composite product of the present invention is a disposableabsorbent pad, which may take various forms, depending upon theparticular use contemplated. Thus, it may be a dressing, an underpad, adiaper or the like. It may be designed to absorb and hold body fluidsand, as desired, may or may not prevent the passage thereof to theoverlying external surface.

The pad may comprise, for example, a top or facing sheet and a bottom orbacking sheet, both fabricated from a water-permeable, waterdispersible, non-woven fabric bonded together by a polymer of thepresent invention, as above indicated. The space between the facingsheet and the backing sheet may be filled with an inexpensive readilydispersible disposable absorbent such as, for example, wood pulp or thelike. If light bonding of the absorbent is desired, the polymericcomposition of the present invention may be used for such purposes.

Alternatively, the backing sheet may comprise a water-impervious sheetsuch as the laminate of film and low wet strength paper above described,with the paper on the outside or exterior. In all embodiments, thefacing sheet and the backing sheet are advantageously bonded together bythe simple technique of heat sealing to the thermoplastic polymeradjacent the contacting peripheries.

THE DRAWINGS

The present invention, particularly the composite product embodimentsthereof discussed above, may be more clearly understood from thefollowing description read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a top plan view of a sheet of film prepared from asilane-crosslinked polymeric composition of the present invention;

FIG. 2 is a top plan view of the sheet of film of FIG. 1 cut as a blankfor forming a bedpan liner;

FIG. 3 is a perspective view of a bedpan liner formed from the sheet ofFIG. 2;

FIG. 4 is a perspective view of a bedpan with the liner of FIG. 3supported therein;

FIG. 5 is an elevation view illustrating a step in the formation of abag from the film of FIG. 1;

FIG. 6 is an elevation view with parts cut away of the completeddisposable bag being formed in FIG. 5;

FIG. 7 is a perspective view illustrating a polymeric film and a paperweb which are subsequently laminated to form a composite structure ofthe present invention;

FIG. 8 is a perspective view illustrating a bedpan prepared from thecomposite structure formed by laminating the film and paper of FIG. 7;

FIG. 9 is an elevation view with parts cut away illustrating adisposable bag prepared from the composite structure formed bylaminating the film and paper of FIG. 7;

FIG. 10 is a perspective view illustrating a non-woven fabric preparedusing the polymeric composition of the present invention as a bindertherefor;

FIG. 11 is a perspective view similar to FIG. 10 but illustrating adifferent binder pattern for the polymer deposits;

FIG. 12 is a perspective view with parts cut away of an absorbent padfabricated in part from the composition of the present invention; and

FIG. 13 is a sectional view along the line 13--13 of FIG. 12.

It should be understood that the structures are represented in thedrawings by graphic symbols and that the drawings are not necessarily toscale. As a result, the representations may depart in certain respectsfrom the actual appearances of the various constructions.

Referring to FIG. 1, a sheet 10 of silane crosslinked interpolymer ofthe present invention is cast as a film as described hereinabove, saidfilm typically having a thickness of about 5 mils. In a preferredalkaline labile embodiment, sheet 10 comprises a silane crosslinkedcopolymer of ethyl acrylate and acrylic acid, 3-(trimethoxysilyl)-propylmethacrylate being the crosslinking monomer. The film contains about 5percent by weight, based on copolymer, of glycerine and 5 percent byweight, based on copolymer, of lauric acid, whereby the sheet is readilyremoved from the casting surface and is flexible and conformable tovessels or containers in which it may be placed.

The four corners of sheet 10 are cut out as indicated by referencenumeral 12 in FIG. 2, preparatory to forming the sheet into a bedpanliner. The outer portions are folded along dashed lines 14 and 16 andheat sealed at the edges thereof to form the bedpan liner 18 illustratedin FIG. 3, said liner having bottom wall 19, vertical side walls 20 andhorizontal edge portions 22.

In use, liner 18 is inserted into bedpan 24, as illustrated in FIG. 4,the bottom wall, side walls and edge portions of the liner conforming tothe corresponding portions of the bedpan. After body exudate isdeposited in the bedpan, all that is necessary for disposal is to carrythe bedpan to a toilet, deposit the liner with the contents thereof intothe toilet, add caustic, and, after two to three minutes, flush thecontents, the liner having dissolved by that time.

FIGS. 5 and 6 illustrate another embodiment of the present inventionemploying the silane crosslinked interpolymer in film form, a disposablebag such as might be employed for receiving urine. As illustrated inFIG. 5, a sheet of film 28 is folded over, and overlapping edges 30 and32 are heat sealed to form an open-ended tube. The bag is completed byheat sealing the bottom to form seal 34 shown in FIG. 6.

In like manner, other disposable liners, bags and the like can beprepared, as will be apparent to those skilled in the art who wish totake advantage of the unique water impermeable nature of the film ofthis invention and its ready disposability in aqueous alkalinesolutions. Numerous composite products may also be prepared asillustrated in the remaining drawings.

Referring to FIG. 7, a film 40 of the present invention may be laminatedby heat and pressure to low wet strength paper 42, typical laminatingconditions being a temperature of 50°-60°C, a pressure of 50 psi, and alaminating dwell time of one second. The laminated structure is cut andfabricated into a bedpan 44 comprising inner film 40a and outer paper42a, as illustrated in FIG. 8. Bedpan 44 may optionally beself-supporting, in which case the film and paper thicknesses and othercharacteristics are selected to achieve the requisite strength andstiffness. As shown in FIG. 8, the paper layer 42a is disposed on theexterior so that the moisture-impermeable barrier provided by film 40aseparates the moisture sensitive paper and the liquid contents of thebedpan.

Likewise, a urine collection bag similar to that of FIG. 6 may also befabricated from the film-paper composite, as illustrated in FIG. 9. Bag46 is heat sealed together with film 40b of the laminate on the interiorand the low wet strength paper 42b on the exterior, the side seal (notin overlapping relationship) being indicated by reference numeral 47 andthe bottom seal being indicated by reference numeral 48. Film 40bprevents contact between the liquid contents and the low wet strengthpaper. The dry strength of the paper thus minimizes extensibility andotherwise strengthens the bag.

Referring to FIG. 10, there is illustrated a non-woven fabric 50 whichcomprises water dispersible, biodegradable non-woven fibers 52 "spotbonded" together by a plurality of discrete polymeric deposits 54,comprising a preferably alkaline soluble, silane crosslinkedinterpolymer of the present invention. Similarly, in FIG. 11 there isillustrated a non-woven fabric 56 which comprises water dispersible,biodegradable non-woven fibers 58 bonded together by discrete polymericdeposits 60 which are located and configured in the articulatedmultisegmental binder pattern of the aforementioned U.S. Pat. No.2,705,687.

As already indicated, the fibers of fabrics 50 and 56 may be"unoriented" or "oriented", e.g., substantially "parallelized", asdesired for specific applications. Instead of the preferred "spotbonding", the silane-crosslinked polymeric binder may be distributedthroughout the fiber web. All embodiments of the non-woven fabrics 50and 56 are, however, completely disposable and flushable, ascontemplated by the present invention.

A completely-disposable absorbent pad suitable for use as an underpad,diaper or the like is illustrated in FIGS. 12 and 13. The top or facingsheet 70 may be prepared, for example, from the non-woven fabricsalready described in connection with FIGS. 10 and 11. While theindividual non-woven fibers and polymeric deposits may not be readilydetectable to the casual viewer, they are indicated in the cutawayportions of FIG. 12 by reference numerals 72 and 74, respectively,solely for purposes of illustration. Likewise, while the fiber layer 72and polymeric deposits 74 are shown discretely for purposes ofillustration in the sectional drawing of FIG. 13, the deposits areactually intermingled with the fibers at the deposit locations.

Non-woven fabric 70 is laminated at its periphery, e.g., by applicationof heat and pressure, to the bottom or backing sheet 80 comprising afilm-paper laminate similar to that described in connection with FIGS.7-9. The film portion 82 of laminate 80 comprises a polymericcomposition of the present invention and is disposed on the interior andthe low wet strength paper 84 is disposed on the exterior. The spacebetween facing sheet 70 and backing sheet 80 is filled with aninexpensive, water-dispersible absorbent 90 such as wood pulp or thelike. If bonding of absorbent 90 is desired, the polymeric composite ofthe present invention may be added thereto for such purposes.

In use, body exudates pass through permeable facing sheet 70 andsaturate absorbent 90. No moisture penetrates backing sheet 80 becausefilm 82 is a water barrier. The paper outer layer 84 provides drystrength to the composite and non-blocking characateristics to thesurface. The entire structure, however, is readily disposable andflushable in accordance with the present invention.

EXAMPLES

The present invention will be more clearly unerstood from the followingspecific examples of certain embodiments which have already beengenerally described and illustrated hereinabove.

EXAMPLE 1 -- ALKALINE SOLUBLE FILM

A polymerization vessel was fitted with a condenser, stirrer,thermometer and nitrogen inlet tube. The vessel was charged with 280parts by weight of ethyl acrylate, 120 parts of acrylic acid, 4.0 partsof 3-(trimethoxysilyl)-propyl methacrylate, 406 parts of ethyl acetateand 138 parts of isopropanol. The solution was stirred and swept withnitrogen while raising the temperature to 75°C. Then 1.0 part of2,2-azobis-(2-methylpropionitrile) was added and the nitrogen flowdiscontinued. Polymerization began and the solution refluxed vigorouslyat 86°C. After the exothermic polymerization had subsided, stirring andheating of the reaction mixture at 80°C was continued for 3.5 hours. Thesolution was then diluted with 388 parts of isopropanol and cooled.Solids content of the solution was 30%.

To 300 parts of the 30% solution were added 4.5 parts of glycerineplasticizer and 0.45 part of dibutyl tin di-2-ethylhexoate catalyst. Atwo-coat film was cast on siliconed paper, with air drying betweencoats. After air drying the second coat, the film was further dried inan oven at 75°C for 15 minutes and then stripped from the siliconedpaper as a single film.

The resulting film was found to be about 5 mils in thickness. When usedas the liner in pans, dishes or bags, it holds water without leaking formore than 24 hours. It is soluble in alkaline solutions and flushable inconventional toilet systems.

The following table summarizes the time required for swatches of thefilm to dissolve in various base solutions.

    ______________________________________                                                                      Time to                                         Reagent   Estimated           Dissolve,                                       Wt. %     pH                  Minutes                                         ______________________________________                                        SODIUM HYDROXIDE                                                              8.0       14.3                5                                               4.0       14.0                5                                               2.0       13.7                4                                               1.0       13.4                4                                               0.5       13.1                5                                               0.25      12.8                18                                              SODIUM CARBONATE                                                              10.0      12.1                9                                               5.0       12.0                8                                               2.5       11.8                8                                               1.0       11.6                12                                              AMMONIUM HYDROXIDE                                                            10.0      12.0                10 to 15                                        5.0       11.8                10 to 15                                        ______________________________________                                    

EXAMPLE 2 -- ALKALINE SOLUBLE FILM

The polymerization of Example 1 was repeated using the crosslinkingmonomers shown in the following table. Essentially quantitativeconversions of monomer to polymer were obtained in each case as shown bythe non-volatile solids content of the solution after polymerization.

Crosslinking of the respective 30% solids solutions was effected byadding 0.5% by weight, based on polymer, of dibutyl tindi-2-ethylhexoate catalyst to the polymer solution, casting the solutionon polyethylene, and drying first at room temperature and then at 75°Cfor 15 minutes. Gel content of the crosslinked polymers was measured bydissolving crosslinked film in ethyl acetate and screening the insolublematerial from the solutions, the solutions having been prepared byallowing 0.5 gram samples of polymer to stand at room temperature for 48hours in 50 ml. of ethyl acetate. The results are as follows:

                                        Water Barrier                                                   Solids, Gel,  properties of                             Crosslinked Agent                                                                          Parts*   Wt.%    Wt.%  2-mil Films                               ______________________________________                                        3-(trimethoxysilyl)-                                                                       0        29.9     None Poor                                      propyl methacrylate                                                                        0.25     29.6    --    Poor                                                   0.50     29.9    --    Poor                                                   1.0      29.6    64.   Excellent                                 Allyl Triethoxysilane                                                                      1.0      30.0    43.   Poor                                                   2.0      29.7    71.   Poor                                      Vinyl triethoxysilane                                                                      1.0      29.7    53.   Poor                                      Vinyl triacetoxysilane                                                                     1.0      29.9    48.   Poor                                      ______________________________________                                         *Parts per 100 parts by weight of ethyl acrylate and acrylic acid        

EXAMPLE 3 -- ALKALINE SOLUBLE FILM

A polymer solution of 30% solids content was prepared as in Example 1. Aportion (150 parts by weight) of the solution was mixed with 0.22 partof dibutyl tin di-2-ethylhexoate and cast as a film onpolyethylene-coated paper. Casting was regulated so as to give a filmthickness after drying of about 2 mils. The film was heated for 15minutes at 75°C after air drying at room temperature for an hour. Underconditions of 25 to 50% relative humidity, this film cracks when flexed.

Another portion of the same 30% solids solution was mixed with 0.22 partof dibutyl tin di-2-ethylhexoate, 2.25 parts of glycerine and 2.25 partsof lauric acid. A 2-mil film was cast and dried from this solution also.It was found that this film is removed more easily from the polyethylenesubstrate and that it has no tendency to crack when flexed underconditions of 25 to 50% relative humidity. The film has excellentimpermeability to water. Portions of the film dissolved readily in 0.5%sodium hydroxide water solutions.

EXAMPLE 4 -- ACID SOLUBLE FILM

A 5-liter, 3-neck flask was fitted with a reflux condenser, mechanicalstirrer, thermometer and nitrogen inlet tube. The following chemicalswere charged to the flask:

    Ethyl acrylate         350     grams                                          N-isopropylacrylamide  150     grams                                          N,N-dimethylaminoethyl                                                         methacrylate          500     grams                                          3-(trimethoxysilyl)-                                                           propyl methacrylate   10      grams                                          Ethyl acetate          1000    grams                                      

The flask was immersed in an electrically-heated oil bath and thecontents stirred and swept with a slow stream of nitrogen. The solutionreached a temperature of 75°C in 30 minutes, at which point 2.55 gramsof 2,2'-azobis-(2-methylpropionitrile) were added and the nitrogenturned off. The temperature then rose to 89°C, at which pointpolymerization proceeded smoothly as the solvent refluxed. After thevigorous reaction subsided, the temperature was allowed decline eclineto 75°-80°C. The reaction mixture was maintained at this temperature andstirred until the total reaction period amounted to 4 hours. Thereaction mixture was then cooled and found to have a polymer content of48.3%.

A 282 gram portion of the reaction mixture was diluted with 59 grams ofisopropanol and 59 grams of toluene, and 0.68 gram of dibutyl tindi-2-ethylhexoate dissolved in 2 ml. of toluene was added. The solutionwas then spread in a smooth layer on silicone-coated paper. The film wasdried first at room temperature, then at 60°C, and finally for an hourat 75°C. The thickness of the dried film was 5 to 6 mils. A second coatwas applied and dried in the same way, bringing the film thickness tothe 10 to 12-mil range. The film was then stripped from the siliconedpaper.

In a dry state, the film is clear, flexible and has a surface which isslightly cohesive. Under humid conditions the surface becomes a littlemore cohesive due to moisture absorption. The film will block to itselfon long standing and is stored with an interliner, e.g., siliconedpaper.

The film is insoluble in urine and in aqueous solutions which are notstrongly acid. It rapidly breaks up and dissolves in hydrochloric acidof 4 to 6 normal concentration (12 to 18% HCl).

Urine bags having holding capacities of about 125 ml. were made from thefilm. If a single 10 to 12-mil thickness was used to make the bag, thewet film in the filled bag stretched enough to cause breakage after 12to 18 hours. A slower rate of stretching occurred if two 10 to 12-milthickness of film were used to make the bag, a two-layer prototypeholding urine for 24 hours without pronounced stretching. But,ultimately, stretching of the double layer bag became just as bad aswith a single layer bag. The dry film shows no stretching at all under a125-gram dry load.

EXAMPLE 5 -- ADDITIONAL ACID SOLUBLE FILMS

A series of acid soluble films was prepared substantially as describedin Example 4, except that the proportions of ethyl acrylate ("EA"),dimethylaminoethyl methacrylate ("DMAEMA"), N-isopropylacrylamide("NIPAM") and 3-(trimethoxysilyl)-propyl methacrylate ("3-TPM") werevaried. Properties of the films, which were cured for 1 hour at 75°Cwith 0.5% by weight, based on polymer, of dibutyl tin di-2-ethylhexoate,are set forth in the following table.

    __________________________________________________________________________    Polymer Composition,                                                          Parts by Weight                                                               Run                                                                              EA    DMAEMA                                                                              NIPAM 3-TPM            Properties of Cured                     __________________________________________________________________________                                          Film                                    1  75    25    --    0.4   Tacky, flexible cohesive.                          2  50    50    --    0.4   Tacky, very flexible.                              3  25    50    25    0.4   Stiff and boardy. Disintegrates and dissolves                                 in 2NHCl within a                                                             few minutes. Insoluble in distilled water and                                 1.5% NaCl.                                         4  52.5  25    22.5  1.0   In 2NHCl film swelled and became thin and soft                                but did not dis-                                                              solve. Insoluble in distilled water and 1.5%                                  NaCl.                                              5  52.5  25    22.5  0.5   In 2NHCl film swelled strongly and became very                                soft, dissolving                                                              completely in about 4 hours. Film was                                         insoluble in distilled                                                        water and 1.5% NaCl.                               6  35    50    15    2.0   Reaction mixture gelled during                                                polymerization.                                    7  35    50    15    1.0   Flexible film having surfaces slightly                                        cohesive. In 2NHCl film                                                       disintegrates in about 15 minutes and                                         dissolves completely on                                                       standing overnight. Film is insoluble in                                      distilled water and                                                           1.5% NaCl.                                         8  35    50    15    0.5   Like film of Run 7 in appearance and feel. In                                 2NHCl it dissolved                                                            completely in less than one hour. Film was                                    insoluble in water                                                            but became very soft, spongy and highly                                       swollen after two days.                                                       In 1.5% NaCl the film became softer than film                                 of Run 7.                                          9  35    50    15     0.25 Like film of Run 7 in appearance and feel. In                                 2NHCl it disinte-                                                             grated in 10 to 15 minutes and dissolved                                      completely in about 20                                                        minutes. Film was insoluble in water but                                      became very soft, spongy                                                      and highly swollen after two days. In 1.5%                                    NaCl the film became                                                          softer than films of Runs 7 and 8.                 10 --    80    20    2.0   Reaction mixture gelled during                                                polymerization.                                    11 --    80    20    1.0   Film was a little less flexible than film of                                  Run 7. In 2NHCl it                                                            disintegrated after soaking for a few minutes                                 and dissolved com-                                                            pletely within 30 minutes. In distilled water                                 alone the film dis-                                                           solved on standing overnight. In 1.5% NaCl the                                film did not                                                                  dissolve but became swollen and too weak to                                   handle.                                            __________________________________________________________________________

The data in the foregoing table indicate that N-isopropylacrylamideeliminates surface tack and that 50% dimethylaminoethyl methacrylate isabout the right amine composition. Polymers with 25% dimethylaminoethylmethacrylate are not sufficiently acid soluble, while those containing80% dimethylaminoethyl methacrylate are too hydrophilic, dissolve inwater, and therefore are not water barriers.

The data also indicate that optimum crosslink density is obtained withabout 1.0 part of 3-(trimethoxysilyl)-propyl methacrylate per 100 partsof other monomers. Less silane leads to polymers which are toowater-sensitive and which lack wet strength. If the silane concentrationis as high as 2.0 parts per 100 parts of monomer, gelation occurs duringpolymerization.

The effect of silane concentration on polymer solubility is shown fromthe following data obtained on the polymers from Runs 7, 8 and 9. Ineach of these runs the other monomers are 35 parts of ethyl acrylate, 15parts of N-isopropylacrylamide and 50 parts of dimethylaminoethylmethacrylate, as indicated in the previous table.

    ______________________________________                                        Source              Solubility, %                                             of        Silane,   In       In      In Ethyl                                 Polymer   pts./100  Water    Toluene Acetate                                  ______________________________________                                        Run 7     1.0       0        23      23                                       Run 8     0.5       0        37      36                                       Run 9      0.25     1        66      67                                       ______________________________________                                    

Highly crosslinked, water-insoluble, hydrophilic polymers are hydrogels,if crosslinking density is not so high as to prevent imbibition ofwater. Hydrogels imbibe water, reaching a certain equilibrium waterabsorption. The equilibrium depends on polymer composition, crosslinkdensity, composition of the aqueous swelling liquid, and temperature.For example, the polymer from Run 7 has an equilibrium water absorptionat room temperature in 1.5% sodium chloride solution of 31 to 35% andthe polymer from Run 8,39 to 44%.

EXAMPLE 6--ALKALINE-LABILE FILM AND PAPER COMPOSITE

A 30% solids solution of polymer was prepared as in Example 1. A thincoat of this solution was cast on polyethylene-coated paper. Afterpartial drying of the solvent from the film in air at room temperature,or slightly above, a layer of 3-mil-thick, high-absorbency, no wetstrength tissue paper was smoothed onto the surface of the film. Thepaper had a dry tensile strength of 300 g./inch-width in the machinedirection and 150 g./inch-width in the cross machine direction. Thepaper bonded firmly to the film surface as drying was completed at roomtemperature and by a final 15 minute treatment in an oven at 75°C.Casting of the film was regulated so that the dry film thickness wasabout 2 mils. Thus, the final laminate consists of about 2 mils of filmand 3 mils of tissue paper. The laminate is readily stripped from thepolyethylene substrate.

The 5-mil film-paper laminate is much easier to handle than a 2-mil freefilm. The paper surface of the laminate prevents excessive stretching ofthe thin film and provides a non-blocking surface on one side.

A circular piece of the laminate, 8 inches in diameter, was formed intoa urine collection bag of about 125 cc. capacity by heat sealing thefilm edges around the periphery of a 2.5-inch-diameter rigid ring. Thefilm is readily heat sealable to itself. The paper surface was disposedon the outside or exterior of the bag, so that it would remain dry andcontribute strength to the urine-filled bag.

Bags of this type held urine without leaking for more than 24 hours. Asimilar bag formed of 2-mil free film without the paper fibers does nothave sufficient strength when wetted to hold such weight of urine.

The film part of the film-paper laminate dissolves completely in 0.5weight percent sodium hydroxide solution within 2 minutes afterimmersion.

EXAMPLE 7 -- ALKALINE-LABILE, NON-WOVEN FABRIC

A 30% solids solution of polymer was prepared as set forth in Example 1.A portion of this solution was diluted to 5% solids with a solventcomprising 88 weight percent isopropanol and 12% ethyl acetate. A web of75 weight percent wood pulp and 25% 1.5 denier rayon, supported on ascreen, was saturated with the 5% polymer solution. The excess solutionwas filtered from the web with suction, leaving the wet web with a 168%increase in weight due to pickup of the solution. The wet web was driedin a hot air oven at about 120°F (49°C) and finally given a 1-minuteheat treatment at 300°F (149°C).

An 8.4% add-on of polymer resulted from this treatment. The bonded webis perfectly stable in aqueous solutions having pH values less thanabout 9. The web disintegrates completely within 5 minutes when immersedin a 1% aqueous sodium hydroxide solution.

The above experiment was repeated using a polymer solution of 2.5%solids concentration to impregnate the web. Wet pickup was 166%, and drypolymer add-on was 4.2%. This web is completely disintegrated after 3minutes immersion in 1% sodium hydroxide solution.

EXAMPLE 8 -- ALKALINE-LABILE ABSORBENT PAD

An alkaline-labile film and paper composite was prepared as in Example 6and heat sealed adjacent its periphery to an alkaline-labile non-wovenfabric prepared as in Example 7, with an absorbent batt of wood pulpfibers between the two layers, as illustrated in FIGS. 11 and 12. Theresult was a self-contained, completely disposable absorbent pad whicheffectively retains the absorbed liquid waste and prevents its passageto the exterior surface. The entire unit is toilet flushable afterestablishing the requisite alkaline conditions, i.e., an alkaline pH,preferably above 12, in the toilet bowl.

From the above description, drawings and examples, it is apparent thatthe objects of the present invention have been achieved. While onlycertain embodiments have been described or illustrated, many alternativemodifications and equivalents will be apparent from the abovedescription to those skilled in the art. These and other alternativesand equivalents are considered to be within the spirit and scope of thepresent invention.

Having thus described my invention, what I desire to secure by LettersPatent and hereby claim is:
 1. A film-forming polymeric compositionhaving water-barrier properties at neutral pH's in the range of betweenabout 4.5 and about 8.5 and solubilizable at a pH substantially outsidesaid neutral pH range, said composition comprising a silane-crosslinkedinterpolymer of about 0.5 to 5 parts by weight of a first monomerselected from the group consisting of the alkyl acrylates wherein thealkyl group has from one to eight carbon atoms, and about 1 part byweight of a second monomer selected from the group consisting of acrylicacid, methacrylic acid, fumaric acid, maleic acid, maleic anhydride,itaconic acid, dimethylaminoethyl acrylate, dimethylaminoethylmethacrylate, diethylaminoethyl acrylate, diethylaminoethylmethacrylate, tert.-butylaminoethyl acrylate and tert.-butylaminoethylmethacrylate, and about 0.9 to 1.5% by weight, based on the combinedweight of said first and second monomers, of a crosslinking monomerselected from the group consisting of the silane monomers having thestructural formula: ##EQU2## wherein: R is selected from the groupconsisting of CH₃ --, CH₃ CH₂ --, CH₃ O-- and CH₃ CH₂ O--;R₁ and R₂ areeach selected from the group consisting of CH₃ --and CH₃ CH₂ --; R₃ isselected from the group consisting of H, CH₃ -- and CH₃ CH₂ --; and n is0 or a positive integer not greater than
 8. 2. The polymeric compositionof claim 1 wherein said first monomer is ethyl acrylate and said silanemonomer is selected from the group consisting of3-(trimethoxysilyl)-propyl methacrylate and 3-(trimethoxysilyl)-propylacrylate.
 3. The alkaline soluble polymeric composition of claim 2wherein said second monomer is selected from the group consisting ofacrylic acid, methacrylic acid, fumaric acid, maleic acid, maleicanhydride and itaconic acid.
 4. The acid soluble polymeric compositionof claim 2 wherein said second monomer is selected from the groupconsisting of dimethylaminoethyl acrylate, dimethylaminoethylmethacrylate, diethylaminoethyl acrylate, diethylaminoethylmethacrylate, tert.-butylaminoethyl acrylate and tert.-butylaminoethylmethacrylate.
 5. The polymeric composition of claim 3 wherein saidsecond monomer is acrylic acid.
 6. The polymeric composition of claim 4wherein said second monomer is dimethylaminoethyl methacrylate.
 7. Thepolymeric composition of claim 6 which further comprises atack-diminishing quantity of N-isopropylacrylamide.
 8. The polymericcomposition of claim 1 which further comprises about 1 to 20% by weight,based on the weight of said interpolymer, of a humectant-typeplasticizer.
 9. The polymeric composition of claim 8 wherein saidhumectant-type plasticizer is selected from the group consisting ofglycerin, diethylene glycol, triethylene glycol, propylene glycol,dipropylene glycol and tripropylene glycol.
 10. The polymericcomposition of claim 1 which further comprises about 1 to 20% by weight,based on the weight of said interpolymer, of a plasticizer havingrelease-agent properties.
 11. The polymeric composition of claim 10wherein said plasticizer is selected from the group consisting of lauricacid, myristic acid and palmitic acid.
 12. A film-forming polymericcomposition having water-barrier properties at pH's below about 8.5 andsolubilizable at pH's above about 9, said composition comprising asilane-crosslinked interpolymer of about 1.5 to 4 parts by weight of afirst monomer selected from the group consisting of the alkyl acrylateswherein the alkyl group has from one to eight carbon atoms, and about 1part by weight of a second monomer selected from the group consisting ofacrylic acid, methacrylic acid, fumaric acid, maleic acid, maleicanhydride and itaconic acid, and about 0.9 to 1.5% by weight, based onthe combined weight of said first and second monomers, of a crosslinkingmonomer selected from the group consisting of the silane monomers havingthis structural formula: ##EQU3## wherein: R is selected from the groupconsisting of CH₃ --, CH₃ CH₂ --, CH₃ O-- and CH₃ CH₂ O--;R₁ and R₂ areeach selected from the group consisting of CH₃ -- and CH₃ CH₂ --; R₃ isselected from the group consisting of H--, CH₃ -- and CH₃ CH₂ --; and nis 0 or a positive integer not greater than
 8. 13. The polymericcomposition of claim 1 in the form of a film having a thickness in therange of about 1 to 20 mils.
 14. A method of forming a polymericcomposition having film-forming characteristics such that the resultantfilm has barrier properties at neutral pH's in the range of betweenabout 4.5 and about 8.5 and yet is solubilizable at a pH substantiallyoutside said neutral range, said method comprising the step ofinterpolymerizing at elevated temperatures about 0.5 to 5 parts byweight of a first monomer selected from the group consisting of alkylacrylates wherein the alkyl group has from one to eight carbon atoms,and about 1 part by weight of a second monomer selected from the groupconsisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid,maleic anhydride, itaconic acid, dimethylaminoethyl acrylate,dimethylaminoethyl methacrylate, diethylaminoethyl acrylate,diethylaminoethyl methacrylate, tert.-butylaminoethyl acrylate andtert.-butylaminoethyl methacrylate, and about 0.9 to 1.5% by weight,based on the combined weight of said first and second monomers, of across-linking monomer selected from the group consisting of the silanemonomers having the structural formula: ##EQU4## wherein: R is selectedfrom the group consisting of CH₃ --, CH₃ CH₂ --, CH₃ O-- and CH₃ CH₂ O;R₁ and R₂ are each selected from the group consisting of CH₃ --, and CH₃CH₂ --; R₃ is selected from the group consisting of --H, CH₃ --, and CH₃CH₂ --; and n is 0 or a positive integer not greater than 8; in thepresence of a catalytic amount of a polymerization catalyst therefor.15. The method of claim 14 further comprising forming said film bydiluting the polymerized reaction product to a solids contents of lessthan about 35% with a solvent for said polymerized product, casting theresulting diluted interpolymer reaction product in the form of a thinfilm, removing said solvent, and curing the film.
 16. The method ofclaim 15 wherein said thin film is cast by coating the dilutedinterpolymer reaction product on a release surface, said method furthercomprising the step of separating the dried film from the releasesurface.
 17. The method of claim 15 further comprising the step ofadding a catalytic amount of a promoter of siloxane condensationreactions to said polymerized reaction product prior to casting.
 18. Themethod of claim 14 wherein said polymerization catalyst is2,2'-azobis-(2-methylpropionitrile).
 19. The method of claim 17 whereinsaid promoter is dibutyl tin di-2-ethylhexoate.
 20. The method of claim15 further comprising the step of adding at least one of humectant-typeplasticizer and a plasticizer having release-agent properties to thediluted polymerized product prior to casting said thin film.
 21. Themethod of claim 20 wherein said humectant-type plasticizer is glycerinand said plasticizer having release-agent properties is lauric acid. 22.The method of claim 15 wherein the solvent used in diluting thepolymerized product comprises isopropanol.